DISCOVERY OF 10-MILLISECOND PULSARS IN THE GLOBULAR-CLUSTER 47-TUCANAE

IN the past four years a total of 13 millisecond pulsars have been found in 12 different globular clusters. These pulsars are believed to be old neutron stars that have been spun up ('recycled') in low-mass X-ray binary systems 1, although some may have been formed by the accretion-induced collapse of white dwarfs in binaries 2. The globular cluster 47 Tucanae has an especially dense core, and is therefore a likely site for millisecond pulsar formation. Using the Parkes radiotelescope, we have now detected ten additional millisecond pulsars in 47 Tuc, more than half of which are members of binary systems. Almost half of the known millisecond pulsars and more than a quarter of the known binary pulsars now reside in this one cluster.